From the Of-Course!-Why-Haven't-We-Thought-About-This-Before? Department: A company in the Netherlands has installed what it calls the world's first device that uses the motion ...

From the Of-Course!-Why-Haven't-We-Thought-About-This-Before? Department: A company in the Netherlands has installed what it calls the world's first device that uses the motion of a revolving door to generate energy.

The door in this case is the entrance to the Driebergen-Zeist railway station in the central part of the Netherlands. It's a high-traffic spot -- 8,500 commuters use the station every day.

The door is expected to generate about 6,400 kwh of energy a year, roughly equal to the needs of one household.

So it's nothing huge. But it's a brilliant way to capture energy from an action that's already occurring thousands of times a day.